Technical Field
Embodiments of the present invention relate to a control device for an internal combustion engine.
Background Art
Technology has already been proposed that performs a diagnosis regarding aged deterioration of a port injection valve that injects fuel into an intake port of an internal combustion engine and implements a countermeasure in accordance with the diagnosis result, as disclosed, for example, in JP2011-149364A. According to this conventional technology, specifically, the timing at which a port injection valve actually opens is detected based on an in-cylinder vibration waveform signal during an operation to open the port injection valve. Subsequently, a fuel amount that is actually injected from the port injection valve is estimated based on the detected timing and an energization time period of a driving pulse signal that is supplied to the port injection valve. Next, a rate of change is calculated based on the estimated fuel amount and an initial value of the fuel amount that is previously determined (a fuel injection amount during normal operation of the port injection valve). If the calculated rate of change is equal to or greater than a threshold value, it is diagnosed that the port injection valve is deteriorating with age, and the energization time period of the aforementioned driving pulse signal is corrected.
Further, in JPH9-184437A, technology is disclosed that corrects a driving time of an in-cylinder injection valve that directly injects fuel into a cylinder of an internal combustion engine, based on an in-cylinder pressure during driving of the in-cylinder injection valve. In a case where fuel is injected from the in-cylinder injection valve in a compression stroke, because the in-cylinder pressure changes depending on the position of the piston, the change in the in-cylinder pressure affects the fuel amount that is actually injected from the in-cylinder injection valve. Therefore, according to the conventional technology disclosed in JPH9-184437A, a pressure difference between the pressure of fuel supplied to the in-cylinder injection valve and the in-cylinder pressure at an intermediate timing during a driving time of the in-cylinder injection valve is calculated, and the relevant driving time is extended or shortened based on the calculated pressure difference.